犬貓尿液檢體保存方式對定量細菌培養結果之影響

Abstract

泌尿道感染在獸醫是常見的疾病。細菌性泌尿道感染是依據相關臨床症狀的出現，以及利用定量細菌培養偵測出病原來確診。目前針對定量細菌培養的指引建議尿液檢體在採集後需立即塗盤培養，或是必須冷藏保存並在24小時內塗盤。儘管如此，有些研究仍指出保存方法的差異會影響定量細菌培養的結果，甚至出現結果判定的錯誤。我們研究的主要目的為比較犬貓尿液定量細菌培養在(1)立即培養、(2)保存檢體於室溫24小時後培養以及(3)保存檢體於4度C冷藏24小時後培養三者的差異。另一個目的為找出陽性細菌培養結果和尿檢結果的相關性。 我們共納入49筆貓和30筆犬尿液檢體。貓尿液檢體保存於室溫和冷藏24小時後培養的結果皆和立即培養完全一致。至於犬尿液檢體，冷藏保存24小時後培養的結果和立即培養完全一致，但保存於室溫者有兩筆檢體出現不同的培養結果，然而整體的一致性還是相當高的（kappa 0.84）。膿尿和菌尿的存在在貓和細菌培養陽性結果呈高度相關，膿尿的陽性預測值為89%、陰性預測值為98%，菌尿的陽性預測值為100%、陰性預測值為98%，沒有膿尿和菌尿的存在可以高度排除細菌培養陽性的可能。在犬，膿尿和菌尿有分別為94%和95%的陰性預測值，沒有膿尿和菌尿的存在則可以高度排除細菌培養陽性結果的可能。 研究結果顯示在24小時內運送檢體至院外實驗室的過程中，尿液檢體有無冷藏對於細菌培養的結果不會有顯著的差異，但冷藏會有更準確的結果。除此之外，尿檢中膿尿和菌尿的存在與否可以幫助判斷細菌培養的結果。

Urinary tract infection (UTI) is a common disease in veterinary practice. The diagnosis of bacterial UTI is based on the presence of related clinical signs and detection of pathogens through quantitative bacterial culture (QBC). Current guidelines for QBC suggested that samples should be inoculated immediately or stored under refrigeration and inoculate within 24 hours. Despite this, some studies have shown that storage conditions can affect the result of QBCs and even lead to false results. The major aim of our study was to compare the results of dog and cat urine QBC between (1) immediate streak plate, (2) streak plate after urine sample stored at room temperature for 24 hours, and (3) streak plate after urine sample stored at 4oC for 24 hours. The other aim of the study was to evaluate whether positive bacterial culture results were associated with the results of urinalysis. We included 49 cat urine samples and 30 dog urine samples in our study. QBC results of cat urine samples storing at room temperature and under refrigeration for 24 hours were all consistent with immediately cultured results. As for dog urine samples, those storing under refrigeration for 24 hours had consistent results with immediately cultured results, but two of the urine samples storing at room temperature yielded different results. However, the overall agreement was still high (kappa 0.84). Presence of pyuria and bacteriuria was highly correlated with positive QBC results for cats. Pyuria had positive predictive value of 89% and negative predictive value of 98%; bacteriuria had positive predictive value of 100% and negative predictive value of 98%. The absence of pyuria and bacteriuria could rule-out possibility of positive QBC results in cats. As for dogs, pyuria and bacteriuria had negative predictive value of 94% and 95%, respectively. Absence of pyuria and bacteriuria could rule-out possibility of positive QBC results. The result of this study suggested that there was no significant difference between QBC results of urine samples storing under different temperature within 24 hours. However, samples under refrigeration would yield more accurate results. In addition, presence or absence of pyuria and bacteriuria in urinalysis can help to predict QBC results.